Melody of the Boundary

Kyousuke and Kai are two up-and-coming musicians. However, the day before their big debut, Kai passes away in a terrible traffic accident. Three years later, Kyousuke has all but given up music when his supposedly deceased partner appears before him as if nothing happened. Kai reminds his friend of the magic of music, encouraging him to start playing again. Can Kyousuke overcome his past and bring the color back into his world once more?

(Source: Yen Press)